WASHINGTON--Members of Congress on Thursday said new laws aimed at restricting pornography on peer-to-peer networks might be necessary, as police vowed to step up enforcement efforts.

During a hearing of the House Government Reform Committee, politicians complained of two problems: The allegedly widespread distribution of illegal child pornography on peer-to-peer (P2P) networks, and the ease by which a youth could stumble across sexually explicit files that may be legal for adults but inappropriate for minors.

"We have a rating system for video games. We have a rating system for music," said Rep. Adam Putnam, R-Fl., who suggested a government-mandated system would be appropriate for files on P2P networks. Otherwise, Putnam warned, P2P users could "prey on spelling errors of third graders looking for Pokemon."

The hearing, which featured two secondary-school students testifying about their disturbing P2P experiences, was designed to showcase the release of a pair of reports on the topic. As previously reported by CNET News.com, the government reports warn that P2P networks are exploding with readily accessible pornography--much of which is legal, and some of which is not.

John Netherland, the acting director of the Department of Homeland Security's CyberSmuggling Center, said his office would focus more closely on P2P networks. The center already is "expanding its investigative efforts to encompass this new technology," Netherland said. "Evidence is easily captured and preserved on a real-time basis...for these reasons peer-to-peer file-sharing investigations are likely to increase."

Under federal law, it is illegal to knowingly possess or distribute child pornography. It generally is legal to possess "obscene" materials--defined by the U.S. Supreme Court as sexually explicit materials lacking scientific, literary, artistic or political value--but illegal to distribute them. Magazines such as Hustler or Penthouse are typically not considered obscene, but legal standards vary from state to state.

Rep. Henry Waxman of California, the top Democrat on the committee, asked: "Can anyone on the panel tell us if pornographers are making money by putting pornographic files on the file-sharing programs?"

P2P network operators are getting rich through aiding and abetting porn-swapping, suggested Rep. Christopher Shays, R-Conn., and another committee member told the chief executive of P2P file-trading network Grokster that "for all practical purposes, you're the pornographer. You're the vehicle by which people are doing these things."

Grokster CEO Daniel Rung said his company had cooperated with federal law enforcement in child pornography investigations and would continue to do so. Rung also suggested that parents supervise their children and use filters that "can be set to screen out much of the objectionable materials from the search results."

It's unclear how publishers of sexually explicit material could make money from P2P networks, because there is no mechanism to allow the creator to be paid. One possibility would be using P2P networks to advertise images or videos featuring the address of a Web site that requires a paid subscription.

Randy Saaf, president of P2P-tracking firm MediaDefender, said his investigations of child pornography on P2P networks found over 321,000 files "that appeared to be child pornography by their names and file types," and said that "over 800 universities had files on their networks that appeared to be child pornography."

But MediaDefender, and one of the government studies released on Thursday, reviewed only the file names and not the actual contents of the image files. A similar approach used in a 1995 article that appeared in the Georgetown University law journal drew strong criticism from academics for having a flawed methodology that led to incorrect estimates of the amount of pornography on the Internet.